Light-Emitting Diode Package Assembly

ABSTRACT

An electrical device containing multiple light emitting diode (LED) dies each having respective first and second connectors suitable to receive current through the LED die. A common base layer of a first electrically conductive material has cavities into which at least one LED die is mounted with its second connector electrically connected by a conductive bonding material to the first conductive material of the base layer. One or more over-layer sections of a second electrically conductive material each are electrically connected by a bond to at least one of the first connector of a LED die. And an insulator electrically separates the first conductive material of the base layer from the second conductive material of over-layer sections.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/052,592, filed May 12, 2008, hereby incorporated by reference inits/their entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

COPYRIGHT NOTICE AND PERMISSION

This document contains some material which is subject to copyrightprotection. The copyright owner has no objection to the reproductionwith proper attribution of authorship and ownership and withoutalteration by anyone of this material as it appears in the files orrecords of the Patent and Trademark Office, but otherwise reserves allrights whatsoever.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to light-emitting diode (LED)arrays and the assembly thereof, and more particularly, but notexclusively, to such created in a custom fashion using primarilymechanical processes.

2. Background Art

A light emitting diode (LED) is essentially a PN junction semiconductordiode that emits light when current is applied across positive andnegative leads, terminals, or connectors. By definition, the LED is asolid-state device that passes current without a heated filament, andthus is inherently more reliable. The materials used in the manufactureof the LED determine the color of the light produced. A clear epoxyresin is commonly used to encapsulate the LED or an assembly of LEDs toprotect the dies and the electrical interconnections to them, and toallow light to pass out of the assembly.

The LED is highly efficient (˜90% efficient) for the conversion ofelectrons into photons.

For comparison, incandescent lighting is roughly only 10% efficient,with 90% of the provided energy being converted to heat, and fluorescentlighting is only approximately 50% efficient. Having such highefficiency, technologies based on the LED are viewed as promising tohelp meet our future energy reduction goals.

In the operation of a LED the luminous intensity is roughly proportionalto the amount of current that is supplied, and the higher the currentthe greater will be the light intensity produced, subject to the designlimits of the device and the materials used. The amount of light emittedfrom an LED is quantified by a single point, on-axis luminous intensityvalue (Iv) and LED intensity is specified in terms of millicandela(mcd). In contrast, the light produced by incandescent lamps is usuallyquantified with a value for mean spherical candlepower (MSCP). Thesevalues for LEDs and incandescent lamps are not comparable.

In general, individual LED chips or dies are designed to operate around20 milliamps (mA). Care must be exercised, however, as the operatingcurrent often must be limited relative to the amount of heat in theapplication. For example, a multiple-chip-in-a-package LED deviceincorporating multiple wire bonds and junction points will obviouslyproduce more heat and thus be more affected by thermal stress than willa single-chip-in-a-package LED device. Similarly, LEDs designed tooperate at higher voltages are subject to greater heat. Important designobjectives for LEDs therefore usually include providing for long-lifeoperation at optimum design currents and providing adequate heatdissipation as a defense against thermal degradation.

Presently, solders and soldering processes are commonly used to make theinterconnections between a LED device and its sources of power andground. The use of solders and higher temperature soldering processes,however, are rife with problems. These materials and processes havealways had certain disadvantages, and a number of new trends in theelectronics industry as well as newly emerging applications for LEDs arerevealing or exacerbating other disadvantages, especially for arrays andother assemblies containing many LEDs.

One set of such disadvantages relates to solder materials. Tin/lead typesolders (e.g., Sn63/Pb37) have been widely used since the earliest daysof the electronics industry. Unfortunately, both tin and especially leadhave serious chemical disadvantages. For these two metals, mining theores, refining those ores, working with the refined metals duringmanufacturing, being exposed to substances including these inmanufactured products, and disposing of the products at the ends oftheir life cycles are all potentially damaging to human and animalhealth and to the environment.

Recently human health and environmental concerns about tin/lead typesolders have resulted in the Directive on the Restriction of the Use ofCertain Hazardous Substances in Electrical and Electronic Equipment(commonly referred to as the Restriction of Hazardous SubstancesDirective or RoHS) in the European Union. This directive restricts theuse of six hazardous materials, including lead, in the manufacture ofvarious types of electronic and electrical equipment. This directive isalso closely linked with the Waste Electrical and Electronic EquipmentDirective (WEEE) 2002/96/EC, which sets collection, recycling, andrecovery targets for electrical goods. Together these directives arepart of a growing world-wide legislative initiative to solve the problemof electronic device waste.

To some extent the electronics industry has always been searching for apractical substitute for tin/lead type solders, and legislativeinitiatives like those just noted are now motivating a number ofchanges. Today a common substitute for tin/lead type solders are SACtype solder varieties, which are alloys containing tin (Sn), silver(Ag), and copper (Cu). But this is merely a compromise. Mining,refining, working during manufacturing, exposure from manufacturedproducts, and disposal are still all issues for tin, silver, and copper.Furthermore, SAC solder processes are prone to other problems, such asthe formation of shorts (e.g., “tin whiskers”) and opens if surfaces arenot properly prepared. It follows that the undue use of some materials,like those in solders, are generally undesirable in electronicassemblies, including LED assemblies.

Another set of disadvantages in the solder-based assembly of electronicproducts is the high temperature processes that are inherently required.The use of heat on and around many electronic components has always beenundesirable. As a general principle, the heating of electroniccomponents increases their failure rate in later use and beyond acertain point outright destroys such components. Tin/lead solders meltat moderate temperatures relative to the thermal limits of traditionalmaterials used in electronics manufacture, and their use has generallybeen tolerable for many components. This is not always the same for SACtype solders, which melt a much higher temperatures (e.g., ˜40° C. orhotter). When SAC type solders are used the likelihood of componentdamage is much higher, resulting in assemblies that fail duringpost-manufacturing testing as well as in-the-field failures.Additionally, generating and managing the heat during manufacturing haveincreased energy, safety, and other costs. It therefore follows that theundue use of heat-based manufacturing processes, like soldering, is alsogenerally undesirable in electronic assemblies.

Increasingly yet another set of disadvantages in the solder-basedassembly of electronic products is one related to the “adding” ofmaterials. When a material, like solder, is added between two componentsto hold them together the additional material inherently has to occupysome space. Solders contain higher density metals, thus increasing theultimate weight of electronic products. The use of liquid-statematerials, like liquid stage solder during manufacturing, often requiresdesigning in additional space around leads, terminals, and connectionpads to account for the ability of the liquid to flow easily and topotentially short to other leads, terminals, pads, etc. Liquid soldershave high surface tensions and effects from this also usually requiremajor design consideration. These are all factors that can requireconsideration as designers increasingly strive to miniaturize electronicassemblies. Accordingly, it further follows that the undue use of anyadditional material in manufactured assemblies and in manufacturingprocesses, again like solder, is generally undesirable in the resultingelectronic assemblies.

In addition to the noted disadvantages in the solder-based assembly ofelectronic products, generally, there can be additional problems inparticular in the solder-based assembly of LEDs. For example, in a LEDthe soldering process can be difficult because the ideal substrates forthermal degradation protection are typically good thermal conductors,purposefully being used because they have a high thermal capacity thatwill help keep the LED assembly within in desired temperature rangeduring operation. This creates a significant challenge for solderassembly of LED packages, however, because the package must be raised toan even more elevated temperature to create reliable solder joints andthe necessary temperatures can then degrade or damage the encapsulantused in the manufacture of the LED package. Moreover, exposure tocertain cleaning chemicals may attack the LED surface and causediscoloration.

FIGS. 1-2 will help to illustrate some of the above points, as well ashelp to introduce some additional points.

FIG. 1 (background art) is a cross-section side view of a typical LEDpackage 10 which may be used in conventional LED assemblies. The LEDpackage 10 includes a conventional LED die 12 that has a first connector14, a second connector 16, a P-layer 18, a P-N junction 20, and aN-layer 22. The first connector 14 here is electrically connected to afirst terminal 24 with a conductive lead 26 and the second connector 16is directly electrically connected to a second terminal 28.

A body 30 is further provided that fills multiple roles. For example,the body 30 physically holds the other elements of the LED package 10 infixed relationships. This serves to protect the internal elements of theLED package 10 (i.e., the LED die 12 and the conductive lead 26), toplace and retain the externally communicating elements of the LEDpackage 10 where needed, and generally to facilitate handling of the LEDpackage 10 when mounting it into an electronic assembly or a larger LEDassembly. The body 30 also serves to optically pass the lightwavelengths that the LED die 12 emits. For this the body 30 particularlyhas a face 32 where light from the LED die 12 is primarily emitted fromthe LED package 10. The body 30 may also serve to conduct heat away frominternal elements of the LED package 10. Historically this thermallyconductive role has usually not been an important one, but that is nowchanging, especially for emerging high power LED applications. In viewof all of these roles, the body 30 of the LED package 10 is typically ofa single plastic material, with glass, quartz, or hybrids of materialssometimes also being used.

FIG. 2 (prior art) is a cross-section side view of a conventional LEDassembly 50 that includes the LED package 10 of FIG. 1. The LED assembly50 here is oriented as it is typically manufactured and as it is oftenused, that is, with the light emitting face 32 of the LED package 10oriented upward.

In this orientation the LED assembly 50 is now discussed as generallybeing “built” from the bottom up. An electrically insulting substrate 52is usually always provided, if for no other reason than to physicallysupport an anode trace 54 and a cathode trace 56 as shown. However,optional elements may also be provided in a sub-region 58 below thesubstrate 52. For example, if the substrate 52 is the top mostnon-conductive layer of a printed circuit board (PCB), other layers mayalso be present in this sub-region 58 (e.g. a ground plane or “reverseside” features if the printed circuit board is double sided).

For some emerging applications a feature that may particularly bepresent in the sub-region 58 below the substrate 52 is a heat spreader.The substrate 52 will typically serve to some extent to transfer heat,but it may not be optimal for that. To clarify, the role of a heat sink(which many in the art are more familiar with) and that of a heatspreader are different. Although these elements operate similarly tosome extent, a head sink is optimized to remove thermal energy from aparticular location, typically a point or small location, whereas a headspreader is optimized to distribute and equalize thermal energy acrossan area or large location.

Continuing with FIG. 2, the anode trace 54 and the cathode trace 56 arelocated above the substrate 52. Again, the common PCB serves as a usefulexample here. In a PCB the substrate 52 is usually an electricalinsulating material, the traces 54, 56 are copper foil, and thenecessary pattern of the traces 54, 56 on the substrate 52 is achievedwith silkscreen printing, photolithography, milling, or some othersuitable process.

Of particular interest here is the next higher feature in the LEDassembly 50, a set of solder pads 60. These electrically connect theanode trace 54 to the first terminal 24 and the cathode trace 56 to thesecond terminal 28 of the LED package 10. The solder pads 60 alsophysically connect the LED package 10 to the rest of the LED assembly50, thus holding the LED package 10 in place.

The possible materials in the solder pads 60 have already been discussedelsewhere herein and are legend. It should further be observed here,however, that the solder pads 60 inherently add an additional level ordisplacement layer 62 to the overall LED assembly 50. In applicationswhere the overall thickness of the LED assembly 50 is critical, thisdisplacement layer 62 can be a concern and minimizing or eliminating itcan then be an important goal.

FIG. 2 also stylistically shows thermal flow paths 64 out of the LEDpackage 10 and into the LED assembly 50. As can be seen here, much ofthe thermal energy produced by the LED package 10 passes through thesolder pads 60, with the majority of it flowing through the secondterminal 28 and the cathode trace 56. In some applications this thermalflow can cause serious problems. For instance, if too much heat buildsup in the LED package 10 it may be damaged internally. The solder pads60 tend to be thermally conductive, but they nonetheless lengthen andcomplicate the primary paths that thermal energy must travel to exit theLED package 10. Furthermore, since the flow of thermal energy in thestructures of the LED package 10 and in the overall LED assembly 50 arenot instantaneous, localized heating can result (e.g., in the region atthe second terminal 28 of the LED package 10 in FIG. 2). This canthermally stress the LED die 12, the LED package 10, and the LEDassembly 50. In extreme situations this can cause separation of a solderpad 60 from the first terminal 24, the second terminal 28, or from atrace 54, 56 and such stress can even result in a fracture of the body30 of the LED package 10.

In FIG. 2 the thermal flow paths 64 out the top and sides of the LEDpackage 10 are minimal (as stylistically depicted with lesser weightarrows). There is little that can be done with respect to the top of theLED package 10, since the face 32 here needs to emit the light produced.But the sides of the LED package 10 would appear to be another matter.Unfortunately however, the solder pads 60 tend to interfere with whatcan be done here. Having the sides of the LED package 10 open (as shownin FIG. 2) is desirable when the LED package 10 is soldered into the LEDassembly 50, especially in surface mount device (SMD) embodiments of theLED assembly 50 where surface tension effects of the liquid solder arerelied on to help position the LED package 10. But after soldering, wickregions 66 in the solder pads 60 (also caused by surface tension effectswhen the solder is liquid) usually remain and can interfere with addinga thermal conductor to the sides of the LED package 10 once it is in theLED assembly 50.

In summary, the use of solder materials, the use of heat-based solderingmanufacturing processes, the undue addition of solder material tomanufactured assemblies and these and additional problems particular tothe solder-based assembly of LEDs are all generally undesirable.

BRIEF SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provideimproved light emitting diode (LED) package assemblies.

Briefly, one preferred embodiment of the present invention is anelectrical device. A multitude of light emitting diode (LED) dies areprovided, each having respective first and second connectors that aresuitable for receiving electrical current through the LED die. A commonbase layer is provided of a first electrically conductive material. Thebase layer has multiple cavities into which at least one of the LED diesis mounted such that its second connector is electrically connected by aconductive bonding material to the first conductive material of the baselayer. At least one over-layer section of a second electricallyconductive material is provided, wherein each over-layer is electricallyconnected by a bond to at least one of the first connectors of an LEDdie. And an insulator is provided that electrically separates the firstconductive material of the base layer from the second conductivematerial of the at least one over-layer section.

Briefly, another preferred embodiment of the present invention is aprocess to assemble an electrical device that includes a multitude oflight emitting diode (LED) dies each having respective first and secondconnectors that are suitable for receiving electrical current throughthe LED die. A common base layer is provided of a first electricallyconductive material, the base layer is surmounted by an insulator, andthe insulator is in turn surmounted by at least one over-layer sectionof a second electrically conductive material. A plurality of cavitiesare made that each extend through one of the over-layer sections andfurther through the insulator and into the base layer. At least one ofthe LED dies is mounted into each of the cavities with a conductivebonding material that electrically connects the second connectors of theLED dies to the first conductive material of the base layer.

And, briefly, yet another preferred embodiment of the present inventionis a process to assemble an electrical device that includes a multitudeof light emitting diode (LED) dies each having respective first andsecond connectors that are suitable for receiving electrical currentthrough the LED die. A common base layer is provided of a firstelectrically conductive material, wherein the base layer has a principleside. A number of cavities are made in the principle side of the baselayer. At least one of the LED dies is mounted into each of the cavitieswith a conductive bonding material that electrically connects the secondconnectors of the LED dies to the first conductive material of the baselayer. An insulator is provided over the principle side of the baselayer, except over the cavities. At least one over-layer section of asecond electrically conductive material is provided over the principleside of the base layer, again except over the cavities. And the firstconnectors of the LED dies are each electrically bonded to at least oneover-layer section.

These and other objects and advantages of the present invention willbecome clear to those skilled in the art in view of the description ofthe best presently known mode of carrying out the invention and theindustrial applicability of the preferred embodiment as described hereinand as illustrated in the figures of the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The purposes and advantages of the present invention will be apparentfrom the following detailed description in conjunction with the appendedfigures of drawings in which:

FIG. 1 (background art) is a cross-section side view of a typical LEDpackage which may be used in conventional LED assemblies.

FIG. 2 (prior art) is a cross-section side view of a conventional LEDassembly that includes the LED package of FIG. 1.

FIGS. 3 a-e depict a series of stages in a process flow duringmanufacturer of a representative LED package assembly in accord with thepresent invention.

FIG. 4 is a top view of the completed LED package assembly of FIG. 3a-e.

FIG. 5 is a side view of an alternate LED package assembly in accordwith the present invention.

FIGS. 6 a-e depict a series of stages in a process flow duringmanufacturer of an alternate LED package assembly in accord with thepresent invention.

FIG. 7 is a top view of the completed LED package assembly of FIG. 6a-e.

FIGS. 8 a-e depict a series of stages in a process flow duringmanufacturer of a yet another representative LED package assembly inaccord with the present invention.

FIG. 9 is a top view of another completed LED package assembly in accordwith the present invention.

FIG. 10 is a top view of another completed LED package assembly inaccord with the present invention.

And FIGS. 11 a-b are partial perspective and side views, respectively,showing yet another completed LED package assembly in accord with thepresent invention.

In the various figures of the drawings, like references are used todenote like or similar elements or steps.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention is a light emittingdiode (LED) package assembly. As illustrated in the various drawingsherein, and particularly in the view of FIGS. 3-10, preferredembodiments of the invention are depicted by the general referencecharacter 100. A number of representative variations of LED packageassemblies 100 in accord with the present invention are now described.

FIGS. 3 a-e depict a series of stages in a process flow duringmanufacturer of a representative LED package assembly 100, 300 in accordwith the present invention. [To differentiate from other variations ofthe LED package assembly 100, the variation in FIGS. 3 a-e is referencedspecifically as LED package assembly 300 and a similar convention isused throughout the following discussion.]

In FIG. 3 a the LED package assembly 300 has a metal base 310, aninsulator 312 coating on the top side of the base 310, and a continuousmetal plating or foil 314 covering the top side of the insulator 312.

In FIG. 3 b a number of cavities 316 have been provided in the top sideof the LED package assembly 300, extending through the insulator 312 andthe foil 314 to expose portions of the base 310. The walls of cavities316 here are shown with an optional taper that will help reflect lightfrom edge emitting LED devices away from the die edge and out of thecompleted LED package assembly 300.

In FIG. 3 c a number of LED dies 12 are shown being placed into thecavities 316. The

LED dies 12 are bonded into the cavities 316 with a bonding material 318to hold the LED dies 12 in place and to provide electrical connectionsbetween the second connector 16 of each LED die 12 and the base 310. Oneexample for the bonding material 318 is a conductive adhesive.

Note: While edge emitting LED dies 12 are used in the examples in thisdescription, surface emitting configurations can also be beneficiallyused. Additionally, while a major advantage of the LED package assembly100 is that it can use non-solder bonding materials. This is not arequirement. For example, solder can be used to bond LED dies 12 to leadframes at a stage before encapsulation, with lower risk of thedisadvantages generally applicable to solder-based methods.

While only one LED die 12 is shown in each cavity 316 in FIGS. 3 a-e, itshould be appreciated that one or more enlarged cavities can be providedand that more than one LED device per cavity can also be used, includingLEDs which emit different colors of the visible light spectrum whichmight be combined to create white light or other mixtures of colors.Similarly, while only one layer of circuits are shown, more than onelayer are possible and could be used for lighting individual colorswithin a multiple die cavity construction. Additionally, leaving extraspace in the cavities can allow for another LED to be placed into acavity for rework or repair if the first LED fails to operate properly.

In FIG. 3 d conductive leads 26 have been provided that connect thefirst connector 14 of each LED die 12 to the foil 314. Wire bonding iswidely used for interconnection of semiconductor devices, but anadditional option here for the conductive leads 26 is to provideintegral leads or metal fingers (not shown) in the foil 314 to be downbonded using a tape automated bonding (TAB) system (such a structure isshown in FIG. 7) to make the interconnections to the LED dies 12. Thiscan reduce the material used and the overall cost because the integralleads can be spot plated with a suitable bonding metal (e.g., gold,silver, etc).

In FIG. 3 e the LED dies 12 have been provided with an over coat and/orencapsulation of a transparent or translucent cover material 320. Whilethis cover material 320 is shown here as being contiguous, that is not arequirement and discrete portions of it can also be dispensed over eachLED die 12 This would be of benefit, for example, to make flexible orfoldable instances of the inventive LED package assemblies 300.

FIGS. 3 a-e show the base 310 having a greater thickness than the otherelements, but proportions and thicknesses here are not critical. Forexample, the base 310, the insulator 312, and the foil 314 (and thecover material 320, if present) can all be made relatively thin to makethe final completed LED package assembly 300 flexible and/or formable.

The LED package assembly 100 can be formed into 3D shapes such as tubesor polyhedrons. Regular or custom assemblies can be creates according tothe needs of a customer. Moreover, individual LED package assemblies 100can be fashioned and joined together so as to create large arrays orthree dimensional assemblies (e.g., a geodesic dome comprised ofinterconnected lighting elements).

In case of thin embodiments, the LED package assembly 300 can also beeasily processed in a roll to roll manner to facilitate handling and forease of use in end-device manufacture. It is possible to improve bothflexibility and utility if substantial portions of the material in thebase 310 is removed between the LED dies 12 or if only minimal materialis used in the base 310. The inventive LED package assembly 300 is suchcases can also be bonded to a metal heat sink (not shown) to performsimilarly to an embodiment having a thicker base.

Additionally, embodiments of the inventive LED package assembly 100 canbe made with the LED dies 12 arranged in arrays, and there is also thepotential to create a matrix having rows on one side and columns on theother that allow each LED die 12 in the array to be individuallyaddressed and operated. This obviates the need for a second metal layerlike the foil 314 here. Interestingly, such embodiments can still beconstructed so that the connectors 14, 16 of the LED dies 12 can all beconnected on the top side of the LED package assembly 100 if the edgesare kept clear.

FIG. 4 is a top view of the completed LED package assembly 100, 300 ofFIG. 3 a-e. While the LED dies 12 are shown here arranged in a regularpattern, it is possible to create instances of the LED package assembly100, 300 in a fully custom manner for names, shapes, or other patterns.

FIG. 5 is a side view of an alternate LED package assembly 100, 500 inaccord with the present invention. This LED package assembly 500 may bemade manufactured the same as the LED package assembly 100, 300 exceptthat the cover material 320 of FIG. 3 e is instead here in FIG. 5replaced with a transparent cover 510. The cover material 320 isdesirably of a suitable material (e.g., glass) to seal edges 512 of theLED package assembly 500 to prevent the ingress to the LED dies 12 ofmoisture or gasses such as oxygen.

FIGS. 6 a-e depict a series of stages in a process flow duringmanufacturer of an alternate LED package assembly 100, 600 in accordwith the present invention.

In FIG. 6 a the LED package assembly 600 has a metal base 610 in the topside of which a number of cavities 612 have been provided.

In FIG. 6 b a number of LED dies 12 are shown being placed into thecavities 612. The

LED dies 12 are bonded into the cavities 612 with a bonding material 318to hold the LED dies 12 in place and to provide electrical connectionsbetween the second connector 16 of each LED die 12 and the base 610. Thebonding material 318 here may be the same as that in the LED packageassembly 100, 300 of FIG. 3 a-e.

In FIG. 6 c a laminate 614 has been provided on the top side thatincludes an insulation 616 and metal conductive leads 618 like thoseused for conventional TAB assembly, extending over the LED dies 12.

In FIG. 6 d the conductive leads 618 have been interconnected to thefirst connectors 14 of the LED die 12 at respective bonds 620.

In FIG. 6 e a transparent cover 510 is provided over the LED dies 12 Thecover 510 here may be the same as that in the LED package assembly 100,500 of FIG. 5. Alternately, the cover material 320 of FIG. 3 e may beemployed.

FIG. 7 is a top view of the completed LED package assembly 100, 500 ofFIG. 6 a-e.

FIGS. 8 a-e depict a series of stages in a process flow duringmanufacturer of a yet another representative LED package assembly 100,800 in accord with the present invention.

In FIG. 8 a the LED package assembly 800 has a metal base 810 in the topside of which a number of cavities 812 have been provided.

In FIG. 8 b a number of LED dies 12 are shown being placed into thecavities 812. The LED dies 12 are bonded into the cavities 812 with abonding material 318 to hold the LED dies 12 in place and to provideelectrical connections between the second connector 16 of each LED die12 and the base 810. The bonding material 318 here may be the same asthat in the LED package assembly 100, 300 of FIG. 3 a-e.

In FIG. 8 c a transparent or translucent encapsulant 814 has been placedover the top of the LED package assembly 800, and thus over the LED dies12 and the cavities 812,

In FIG. 8 d a series of apertures 816 have been created in theencapsulant 814, providing access to the first connectors 14 the LEDdies 12.

In FIG. 8 e a conductive coating 818 (e.g., a metal plating) has beenapplied and patterned to make connections to the first connectors 14 theLED dies 12.

FIG. 9 is a top view of another completed LED package assembly 100, 900in accord with the present invention. The LED package assembly 900 hereis made with a deposition process, similar to that which can be used tocreate the LED package assembly 800 in FIG. 8 a-e, only here conductivefingers 910 are provided which are similar to the conductive leads 618in FIG. 6 a-e.

FIG. 10 is a top view of another completed LED package assembly 100,1000 in accord with the present invention. Here multiple top-sideconductors 1010 are provided to the first connectors 14 the LED dies 12.In FIG. 10 only two top-side conductors 1010 are shown, but it should beappreciated that more top-side conductors can also be provided,potentially even as many as one per LED die 12 Any of the process flowapproaches described above for FIGS. 3 a-3, 6 a-e, or 8 a-e can beextended to create the LED package assembly 1000 in FIG. 10.

FIGS. 11 a-b are partial perspective and side views, respectively,showing yet another completed LED package assembly 100, 1100 in accordwith the present invention. The LED package assembly 1100 here includesa reflector 1110 having a reflective surface 1112 is added above the LEDdies 12, to receive light from the LED dies 12 and redirect it along adifferent light path 1114 (represented in FIG. 11 b with dashed arrows).The reflector 1110 can simply be an added foil shell with open space ina region 1116 between the LED dies 12 and the reflective surface 1112.Alternately, especially when it is desirable that the LED packageassembly 100, 1100 be robust and/or able to limit the ingress ofcorrosive gasses (e.g., oxygen) or moisture to the LED dies 12, thereflector 1110 can be make of a solid transparent material in the region1116 with some surfaces of this solid material selectively then coatedwith another material (e.g., silver) that forms the reflective surface1112. The latter case is the one depicted in FIG. 11 a.

Summarizing, we have herein described a process for creating novel LEDpackage assemblies 100 using a minimum number of process steps. The LEDpackage assemblies 100 are produced in a manner where light emittingdevices (LED dies 12) are placed and permanently affixed bothelectrically and mechanically (e.g., using a conductive polymer) intocavities (cavities 316, 612, 812; with at least one light emittingdevice per cavity) in a conductive substrate (the base 310, 610, 810;e.g., a copper or copper coated polymer). The cavities preferably havetapered walls and can optionally be coated with a light reflectivecoating (e.g., silver) to direct light emitted from the edges of the LEDdies outward and away from the cavity and the LED package assembly. Theprocess used creates an electrical connection between the bottom side(second connector 16) of each LED die and the base. The process usedfurther creates another electrical connection between the top side(first connector 14) of the LED die and a metal layer (the foil 314,conductive leads 618, conductive coating 818, or conductive fingers910).

The metal layer (the foil 314, conductive leads 618, conductive coating818, or conductive fingers 910) is separated from the conductivesubstrate (the base 310, 610, 810) by an organic (e.g., resin polymer)or inorganic (e.g., ceramic material) insulating layer (the insulator312 or insulation 616). In the latter case the LED package assembly canbe created from an anodized piece of aluminum having a suitable metalplating over the top of an insulating alumina (Al₂O₃) skin. Theinsulating material may also be at least partially of a voltageswitchable material, to protect the LED package assembly fromelectrostatic discharge.

The inventive LED package assembly 100 may optionally be coated with atransparent encapsulant or provided with an optically clear sealed cover(e.g., glass), as might be required for certain types of LEDs whichoperate in the UV light ranges and where a polymer coating mightdegrade. To protect the LED dies from degradation due to oxidation, atranslucent or transparent cover can be provided that desirably createsa hermetic seal to prevent the ingress of oxygen and moisture. In eitherof the above cases, however, the LED package assembly cam be created toleave one or more areas open to make electrical contact to the topsurface metal layer. To then light the LED package assembly anelectrical source is connected to this top surface contact and thebottom surface (e.g., the bottom of the base with appropriate electricalpolarity and voltage to pass current through all of the LED dies.

Further modifications can be made to the basic structure of the LEDpackage assembly 100 while still staying true to the spirit of thisinvention. For example, the top metal layer (the foil 314, conductiveleads 618, conductive coating 818, or conductive fingers 910) can, ifdesired, be cut, skived or milled into discrete areas so that more thanone section can be made, thus creating more than one lighting circuit.Alternatively, the leads in the top metal layer can be printed directlyon to the LED package assembly using conductive inks to further simplifythe assembly process, if desired. The same can be done on the bottomside of the base if an insulator is applied over that surface. In thelatter case a matrix then is created allowing the user to light one, afew, or all LEDs at one time.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, andthat the breadth and scope of the invention should not be limited by anyof the above described exemplary embodiments, but should instead bedefined only in accordance with the following claims and theirequivalents.

1-17. (canceled)
 18. A process to assemble an electrical devicecomprising a plurality of light emitting diode (LED) dies each havingrespective first connectors and second connectors that are suitable forreceiving electrical current through respective of the LED dies, theprocess comprising: providing a common base layer of a firstelectrically conductive material wherein said base layer has a principleside, the principle side comprising a flat surface; making a pluralityof cavities in said principle side of said base layer; mounting at leastone of the plurality of LED dies into each of said plurality of cavitieswith a conductive bonding material electrically connecting the secondconnectors of the LED dies to said first conductive material of saidbase layer; the LED dies having a top surface with the first conductorslocated in central region; providing a transparent flat insulator oversaid principle side of said base layer, the transparent flat insulatinglayer contacting a top surface of the LED dies but not filling thecavities; forming apertures in said transparent flat insulator exposingthe first conductors but not otherwise exposing the top surfaces of theLED dies; providing at least one patterned flat over-layer of a secondelectrically conductive material over transparent flat insulator, theover-later extending into said apertures and contacting said firstconnectors.
 19. The process of claim 18, wherein: said making includesshaping at least some of said plurality of cavities to receive lightfrom the at least one of the plurality of LED dies mounted therein andreflect said light out of the electrical device.
 20. The process ofclaim 18, wherein: said making includes sizing at least some of saidplurality of cavities to mountably contain more than one of saidplurality of LED dies.
 21. The process of claim 18, wherein: said flatover-layer comprises metal plating.
 22. The process of claim 18, furthercomprising: adding a covering over said plurality of cavities of amaterial transparent to light emitted by the plurality of LED dies. 23.The process of claim 18, further comprising: installing a reflector oversaid plurality of cavities suitable to collectively receive lightemitted by the plurality of LED dies and to redirect said light.